Incidental recall on WAIS-R Digit Symbol discriminates Alzheimer's and Parkinson's diseases

The purpose of this study was to examine how Alzheimers (n = 37) and Parkin son's (n = 21) patients perform on the incidental recall adaptation to the Digit Symbol of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) and how such performance is related to established cognitive efficiency and mem ory measures. This adaptation requires the examinee to complete the entire subtest and then, without warning, to immediately recall the symbols associ ated with each number. Groups did not differ significantly on standard Digi t Symbol administration (90 seconds), but on recall Parkinson's patients re called significantly more symbols and symbol-number pairs than Alzheimers p atients. Using only the number of symbols recalled, discriminate function a nalysis correctly classified 76% of these patients. Correlations between ag e-corrected scaled score, symbols incidentally recalled, and established me asures of cognitive efficiency and memory provided evidence of convergent a nd divergent validity. Age-corrected scaled scores were more consistently a nd strongly related to cognitive efficiency. whereas symbols recalled were more consistently and strongly related to memory measures. These findings s uggest that the Digit Symbol recall adaptation is actually assessing memory and that it can be another useful way to detect memory impairment. (C) 200 1 John Wiley & Sons, Inc.